1. Field
The present disclosure relates to semiconductor fabrication and more particularly to metamorphic High Electron Mobility Transistor (mHEMT) technology.
2. Background
Metalorganic Chemical Vapor Deposition (MOCVD) is a technique that is used to deposit very thin layers of atoms onto a semiconductor wafer, useful in the manufacture of high speed III-V semiconductor devices. The reference to “III-V semiconductor devices” refers to semiconductor devices using elements from groups III and V of the periodic table of elements, such as transistors based on gallium arsenide (GaAs).
III-V semiconductor devices have advantages over silicon-based semiconductor devices in terms of speed and high gain. Because electrons can move very fast in III-V materials, transistors or devices containing III-V semiconductors are useful in applications which require for high speed and low power logic applications due to its high electron mobility. It allows high-speed and low-voltage logic-circuit-block to couple with the current Si—CMOS platform even for future microprocessor applications. III V Field Effect Transistor (FET) devices exhibit high drive current gain over Si CMOS, it retains the high carrier mobility of the Quantum-well FET. III-V based materials on silicon are under consideration for possible replacement of the Si-CMOS devices in future.
In the MOCVD process, source chemicals are vaporized and transported by hydrogen into the reactor together with other gases at typical reaction pressure, temperature. There, a pyrolysis reaction of the vapors of a volatile metal-organic compound and a gaseous hydride, the critical chemical reaction takes place that turns the chemicals into the desired crystal, which is the III-V compound semiconductor. In one existing technique, the Jesus A. del Alamo group (MIT) leads the technology using Molecular Beam Epitaxy (MBE) apparatus. From his result, the devices on InP substrate with gate width (Lg)=50 nm exhibits threshold voltage (Vt)=0.1 V, Peak Gm (Gm,max)=1.75 mS/μm, fT=465 GHz and the maximum unity current gain cut-off frequency (fMax·)=1.06 THz at a moderate value of VDS=0.75 V by MBE. The industry leader, Intel, announced LG=75 nm In0.7Ga0.3As Quantum-well Field Effect Transistor (QWFET) on Si with composite high-K gate stack achieves high transconductance of 1750 μS/μm and high drive current of 0.49 mA/μm at VDS=0.5 V by MBE.